Rapid advances are occurring in various electronic devices especially display devices that are used for various communicational, financial, and archival purposes. For such uses as touch screen panels, electrochromic devices, light-emitting diodes (LED's), field-effect transistors, solid-state illumination, organic light-emitting diode (OLED) displays, and liquid-crystal displays, electrically-conductive films are essential and considerable efforts are being made in the industry to improve the properties of those electrically-conductive films and particularly to improve metal grid or line conductivity and to provide as much correspondence between mask design with resulting user metal patterns.
Electrically-conductive articles used in various electronic devices including touch screens in electronic, optical, sensory, and diagnostic devices including but not limited to telephones, computing devices, and other display devices have been designed to respond to touch by a human fingertip or mechanical stylus.
There is a particular need to provide touch screen displays and devices that contain improved electrically-conductive film elements. Currently, capacitive touch screen displays use Indium Tin Oxide (ITO) coatings to create arrays of capacitive areas used to distinguish multiple points of contacts. ITO coatings have significant disadvantages and efforts are being made to replace their use in various electronic devices.
In known printed circuit board (PCB) and integrated circuit manufacture processes, the preferred means for mass manufacture is to print a circuit directly from a master article onto a suitable substrate, to create a copy of the circuit image on a suitable PCB photosensitive film, or to directly laser-write a master circuit image (or inverse pattern) onto the PCB photosensitive film. The imaged PCB photosensitive film is then used as a “mask” for imaging multiple copies onto one or more photoresist-coated substrates.
An essential feature of these methods is that the PCB photosensitive film and photoresist compositions are optimized in formulation and development so that the imaged copies are as faithful a representation of the master image as possible with respect to circuit dimensions and properties. This property is sometimes referred to as “fidelity” (or “correspondence”) and the worse the fidelity, the poorer the performance of the resulting copies. However, in mass production of these electrical circuits having designed patterns with very fine dimensional features, there are a number of compositional and operational (for example, chemical processing) conditions that naturally work against fidelity, or making faithful reproductions of the master circuit image.
Electrically-conductive silver articles have been described for use in touch screen panels that have electrically-conductive silver grid patterns on both sides of a transparent substrate, for example as in U.S. Patent Application Publications 2011/0289771 (Kuriki) and 2011/0308846 (Ichiki).
However, the mere presence of electrically-conductive silver grid patterns on one or both sides of the transparent substrate is not sufficient to provide a response that is needed for sensing touch for various electronic devices. The electrically-conductive metallic grids must be connected in some manner to each other and to suitable electronic components and software in the devices so that desired functions can be accomplished in response to a touch from a finger or stylus. Thus, electrically-conductive articles are also designed with electrically-conductive “BUS” lines (or electrically-conductive connectors or terminal wiring regions) that are outside the electrically-conductive touch regions designed for touching. One representation of such an electrically-conductive article is shown in FIG. 8 of U.S. Patent Application 2011/0289771 (noted above).
Normally, the electrically-conductive metallic connector in the electrically-conductive article is not designed for high transparency or sensitivity to touch. It will likely have different conductivity and dimensions compared to the electrically-conductive metallic grid in the touch regions. These differences further make it harder to achieve desired fidelity of a master circuit image and copies made therefrom.
Known low-cost methods for making fine wires suitable for apparently-transparent touch regions designed for touching are not always adaptable to making large and thick wires that are suitable for BUS lines used in electrically-conductive metallic connectors or terminal wiring regions that are outside the electrically-conductive touch regions containing electrically-conductive metallic grids. Using different manufacturing methods for each of such regions is costly and prone to various problems.
Thus, there is a need for transparent electrically-conductive articles that have both electrically-conductive metallic grids in touch sensitive regions as well as electrically-conductive metallic connector that are as close to being reproductions to the master circuit image as possible.